A distributed storage system has multiple item servers, and stores items, such as files, emails, photos, or any other type of data. Each item is stored on one of the item servers. An item server could be a single computer, part of a computer (e.g., a partition on the computer's attached storage), several computers cooperating to replicate items, or some combination of these (e.g., a collection of three distinct partitions on three distinct computers might constitute a single item server).
It is sometimes necessary or desirable to move an item from one item server to another, to improve the system's performance or balance the item server storage load, for example. Conventional techniques are prone to failure, especially when a part of the system fails or reboots. For example, with conventional techniques, items are often lost or unintentionally duplicated.